The only one of the 4Cs that is within human control is a diamond's cut. Cut is the result of a craftsman’s skill in transforming a rough diamond into a breathtaking gem. A diamond has facets that allow light to enter it, become refracted, and exit in a rainbow of colors. A better cut diamond does a better job of dazzling us with its beauty. Here’s the ‘secret’ to how a diamond sparkles:
As you can see, the diamond with the correct proportions does a more effective job of refracting light out the top of the stone to your eye. The less-than-ideal cut diamonds allow some light to become lost out the bottom.
There are many measurements that go into creating a diamond that truly maximize the refraction of light. Facets must be cut at exactly the right angles relative to one another; the top and bottom halves of the stone must have the proper depth relative to each other; the table, or flat surface on the top, must be the correct size, relative to the overall size of the stone. And, of course, the facets on the top (crown) and bottom (pavilion) must align correctly with each other. Here is a diagram showing a diamond’s basic proportions:
These measurements and percentages are different for each diamond, and are all taken into account in the evaluation of a diamond’s cut. In fact, each diamond shape (heart, round, oval, emerald, etc.) has its own set of guidelines for what makes a Premium or Good cut.
DIAMONDS - CUT